Container base



FIG. 1 is a front perspective view, from above, of the claimed design;

FIG. 2 is a rear perspective view, from beneath, of the claimed design;

FIG. 3 is a top plan view of the claimed design;

FIG. 4 is an underneath view of the claimed design;

FIG. 5 is a left side view of the claimed design;

FIG. 6 is a right side view of the claimed design;

FIG. 7 is a front view of the claimed design; and,

FIG. 8 is a rear view of the claimed design. 

CLAIM The ornamental design for a container base, as shown and described. 